The publications in this collection do
not reflect current scientific knowledge
or recommendations. These texts
represent the historic publishing
record of the Institute for Food and
Agricultural Sciences and should be
used only to trace the historic work of
the Institute and its staff. Current IFAS
research may be found on the
Electronic Data Information Source
(EDIS)
site maintained by the Florida
Cooperative Extension Service.

INTRODUCTION
Enough research has been done on the physiological functions
of boron in plant tissues to indicate that this element plays
more than 1 important role in metabolic processes. With refer-
ence to boron, manganese and iron, Shive (11)1 has said "... it
is probably safe to assume that each of these elements is a criti-
cal factor in every important physiological process involved in
the nutrition of the plant".
It is nevertheless important that the specific requirements and
roles played by each nutrient element be explored and under-
stood. Studies of the functional roles of boron have not been
well integrated, despite the mass of research work done with
this element. Isolated findings have begun to form a pattern,
however, giving a substantial background for theoretical con-
sideration and direct leads for substantiating research.
Perhaps the most important leads in this connection have
come from the linkage of boron with the utilization of carbo-
hydrates. Several workers, (14), (10), and (6), suggest that
boron deficiency results in a respiratory break-down, with simul-
taneous accumulation of both simple sugars and ammonia nitro-
gen. Phillips (8) reports that the boron level of the tomato
influences the respiratory rate of the fruits.
In addition to this, Reeve and Shive (9) have reported that
at high levels of potassium in the substrate, boron deficiency
symptoms were more severe and appeared sooner than at low
potassium levels. This was in agreement with field-plot findings

1Italic figures in parentheses refer to Literature Cited on page 26.

Florida Agricultural Experiment Station

by White-Stevens (15). Knowing boron to be intimately con-
cerned with sugar utilization and with potassium level, it is
therefore of further interest to note that potassium level also
has been found to be linked with the utilization of simple sugars
by Beckenbach, Robbins and Shive (3) and Steward and
Preston (13). This would seem to complete the pattern linking
boron functionally to the dehydrogenation of sugars or to the
very early stages of nitrogen metabolism, very probably at or
near the same step in the process where potassium functions
with like effect.
Assuming this theory to be valid, at least 1 more finding
relative to boron can be logically linked to this picture. Eaton
(5) has reported boron to be essential to auxin formation in
plants. Since it has further been reported by Avery et al (1)
that nitrogen level practically controls the production of natural
growth hormones in 2 plant species, it becomes a distinct possi-
Sbility that the connection between boron and auxin production
is an indirect result of this same boron-reducing sugar relation-
ship. This would necessarily imply, of course, that there is also
a relationship between boron and nitrogen nutrient levels re-
sulting directly from the more intimate boron-carbohydrate con-
nection. There are general statements to this effect in the
literature, but the author knows of no reference based on direct
tests.
Other literature reporting research work based on functional
relationships of boron would appear to be essentially unrelated
to this pattern. Among these could be included the boron-
calcium investigations which have been reported upon from
time to time, as well as the general water relationships (10).
It would seem that in view of the major function of boron in
assimilatory processes outlined above, such data should be con-
sidered carefully before direct functional connections are as-
sumed. Any element directly concerned with such an important
function as protein synthesis in any of its phases can probably
be connected experimentally with almost any factor which in-
fluences the growth of plants in any manner.

PURPOSE OF THE EXPERIMENT
The prime purpose of this experiment was to attempt to
establish direct evidence of a functional relationship between
boron and nitrogen. Proof of such a connection would go far
to substantiate the theory outlined in the introduction.

Functional Relationships Between Boron and Anions 5

In addition to this, it was decided to vary concentrations of
the sulphate and phosphate ions, since the method decided upon
will permit this without complicating the set-up unduly. There
have been no reports in the literature indicating any connection
between boron requirements and requirements for phosphate or
sulphate. On the other hand, Chandler (4) reports no such
connection in some tests in which boron concentrations were
varied simultaneously with variations in supply of nitrogen,
phosphorus, potassium, calcium and magnesium, within the
limits which he tested. That these limits were not adequate for
a thorough test is indicated by the fact that Reeve and Shive (9)
have since shown a positive functional linkage between boron
and potassium. It was therefore thought possible that the same
might hold true in Chandler's comparisons of boron level with
the anion levels.

EXPERIMENTAL PROCEDURE
The Solutions Used.-A series of nutrient solutions funda-
mentally similar to those originally designed and reported by
Beckenbach, Wadleigh and Shive (2) was used. In this instance,
only the 3 anions (NOs-, H2PO4- and S04=) were varied, with the
cation concentrations (K+, Ca++, and Mg++) being held con-
stant for all solutions. The make-up of the solutions was further
modified in that all ionic concentrations were calculated on the
basis of milliequivalents rather than on a basis of partial-volume-
molecular concentrations. The cations were supplied to all
treatments so that all received 8 m.e. K+, 5 m.e. Ca++, and 5 m.e.
Mg++ per liter. The constant drip technique of Shive and Stahl
(12) was used with sand cultures. The important fact in such
a series is that the relative concentrations of ions of like charge
may be varied without introducing another ion of opposite
charge, and that the total solution concentration remains about
the same. A further discussion is given in detail in the paper
referred to above (2).
The anionic balance was varied to give 7 different treatments,
as indicated in Table 1. Boron treatments were varied at 4
levels within each of these treatments. The 7 lettered main-
plot anion treatments were thus sub-divided into 4 sub-plot boron
treatments, making 28 treatments in all. The boron levels were:
1) No boron, 2) 0.005 p.p.m. boron, 3) 0.5 p.p.m. boron, and 4)
10.0 p.p.m. boron. Boron was supplied as boric acid. In addi-
tion to the nutrients listed above, manganese (from manganous

TABLE 1.-THE MILLIEQUIVALENT PROPORTIONS OF ANIONS AND THE NUM-
BER OF P.P.M. OF BORON (FROM BORIC ACID) USED IN MAKING UP THE
VARIABLE ANION X VARIABLE BORON SERIES SOLUTIONS. ALL SOLUTIONS
CONTAIN 8 M.E. K+, 5 M.E. CA', AND 5 M.E. MG++ PER LITER, AND
ALL DATA ARE ON THE LITER BASIS.

Salts used were either Bakers Analyzed or Merck Reagent
grade. All water was distilled through a Barnstead hardwater
still, and all solutions made up and kept in soft glass.
Two complete replications of 28 treatments each were used
on opposite sides of the greenhouse. The lettered main-plot

Functional Relationships Between Boron and Anions 7

series were arranged at random and the numbered sub-plot
treatments were randomized within the main plots.
History of the Test Plants.-Seed of the Rutgers variety were
sown in good potting soil on Feb. 10, 1943. Uniform seedlings
were selected 6 days later with only cotyledonary leaves de-
veloped, and set 1 to a 2-gallon glazed coffee-urn lining in acid
and distilled water washed quartz sand. Each plant received
1 liter of T-3 solution (balanced anion, 0.5 p.p.m. boron) at the
time of setting. They were continued on this formula for 8
days, at which time the plants were sturdy and uniform in ap-
pearance. At this time (February 24) the differential anion
treatments were begun and the plant heights, in centimeters,
were recorded. All plants continued to receive boron at 0.5
p.p.m. until the first blooms opened on March 8. The differ-
ential boron treatments were started on that date.
Up until this time, while the plants were small, each received
1 liter of solution per day by the constant drip method. When
the'boron treatments were started, each plant received, in addi-
tion, 1 liter of solution every other day which was poured
directly through the sand. Later, as the plants became larger,
they were each flushed with 1 liter of solution every day, in
addition to the liter applied by the constant drip method.
Side-shoots were pruned from the cotyledonary axils and from
the axils of the first 2 true leaves. Thereafter they were per-
mitted to develop. Treatments were continued until April 6,
when growth records were taken, photographic records were
made and the series was discarded. They had been on differ-
ential anion treatments for 41 days and on differential boron
treatments for 29 days.
Records of height increases were taken from time to time as
the plants grew; also notes on the appearance of any symptoms
of abnormality and other pertinent observations.

APPEARANCE OF VISIBLE SYMPTOMS OF NUTRITIONAL
DISORDERS
Symptoms Associated with Boron Level.-Boron toxicity
symptoms appeared very soon on some plants. By 1 week from
the time when differential boron treatments were begun, symp-
toms were already severe in Series T, U, W, Y and Z. Within
the next few days they appeared in Series V, and finally, some
days later, in Series X. The higher the nitrate, the more severe

Functional Relationships Between Boron and Anions 7

series were arranged at random and the numbered sub-plot
treatments were randomized within the main plots.
History of the Test Plants.-Seed of the Rutgers variety were
sown in good potting soil on Feb. 10, 1943. Uniform seedlings
were selected 6 days later with only cotyledonary leaves de-
veloped, and set 1 to a 2-gallon glazed coffee-urn lining in acid
and distilled water washed quartz sand. Each plant received
1 liter of T-3 solution (balanced anion, 0.5 p.p.m. boron) at the
time of setting. They were continued on this formula for 8
days, at which time the plants were sturdy and uniform in ap-
pearance. At this time (February 24) the differential anion
treatments were begun and the plant heights, in centimeters,
were recorded. All plants continued to receive boron at 0.5
p.p.m. until the first blooms opened on March 8. The differ-
ential boron treatments were started on that date.
Up until this time, while the plants were small, each received
1 liter of solution per day by the constant drip method. When
the'boron treatments were started, each plant received, in addi-
tion, 1 liter of solution every other day which was poured
directly through the sand. Later, as the plants became larger,
they were each flushed with 1 liter of solution every day, in
addition to the liter applied by the constant drip method.
Side-shoots were pruned from the cotyledonary axils and from
the axils of the first 2 true leaves. Thereafter they were per-
mitted to develop. Treatments were continued until April 6,
when growth records were taken, photographic records were
made and the series was discarded. They had been on differ-
ential anion treatments for 41 days and on differential boron
treatments for 29 days.
Records of height increases were taken from time to time as
the plants grew; also notes on the appearance of any symptoms
of abnormality and other pertinent observations.

APPEARANCE OF VISIBLE SYMPTOMS OF NUTRITIONAL
DISORDERS
Symptoms Associated with Boron Level.-Boron toxicity
symptoms appeared very soon on some plants. By 1 week from
the time when differential boron treatments were begun, symp-
toms were already severe in Series T, U, W, Y and Z. Within
the next few days they appeared in Series V, and finally, some
days later, in Series X. The higher the nitrate, the more severe

Florida Agricultural Experiment Station

the toxicity and the sooner symptoms appeared. Relative pro-
portions of phosphate to sulphate had some effect also, since
Series V seemed less severely hurt than W, and Series Z seemed
less severely hurt than Y. In both of these comparisons the
treatments compared received the same amounts of nitrate.
Boron deficiency symptoms appeared shortly after the appear-
ance of toxicity symptoms. These also were most severe at
high nitrate levels, and never did appear in Series X which re-
ceived no nitrate, and Series V, which received low nitrate, low
sulphate and high phosphate. Since Series W showed boron
deficiency, it was evident that 1 of the anions other than nitrate
also influenced the appearance of boron deficiency. When nitrate
and phosphate were low, but sulphate high, boron deficiency
symptoms appeared. When nitrate and sulphate were low and
phosphate high, no boron deficiency symptoms appeared.
Series Y and Z, both receiving 9 m.e. nitrate per liter, showed
differences in boron deficiency symptoms. Plants receiving no
boron and no phosphate (Y-l) got bushy and brittle at .the
growing point, and the fruits mostly blackened and abscised.
Plants receiving no boron and no sulphate (Z-1) did not get
bushy, although elongation of the growing point was somewhat
slowed down, and boron deficiency symptoms appeared on the
fruits (brown cork around the stem end); fruits did not abscise.
When phosphate was high and sulphate low, boron deficiency
was less severe than when the reverse was true, irrespective
of nitrate level.
In addition, since boron deficiency symptoms appeared in both
U-2 cultures where 0.005 p.p.m. boron was constantly supplied,
it is evident that when nitrates are very high the boron require-
ments are also high. It was, therefore, indicated from the ap-
pearance of symptoms that boron requirements were dependent
on concentrations of at least 2 of the anions under study.
Symptoms Associated with Anionic Balance.-The most con-
spicuous symptoms developed under this heading were those
associated with the nitrogen supply. Plants receiving no nitrate
and plants receiving only 1 m.e. of nitrate per liter (out of the
total anionic solution content of 18 m.e.) showed unmistakable
symptoms of nitrogen deficiency. When no nitrogen was sup-
plied the plants became spindly, no lateral shoots developed, leaf-
lets throughout were small and pale green with purple veins, and
the older leaves turned yellow and finally died. Only 1 or 2
fruits developed when no nitrogen was supplied- further

Functional Relationships Between Boron and Anions 9

blooms abscised. The fruits remained small. Where 6 or more
m.e. of nitrate were supplied, the plants developed vigorous
side-shoots, the color was a good green, and fruits set well on
all clusters and made excellent size, except where other con-
trolled deficiencies interfered.
The only plants showing phosphate deficiency symptoms were
those which received no phosphate. Since this series of plants
received ample nitrogen (9 m.e. per liter), they grew vigorously
throughout the test. Leaves were a deep bluish-green however,
and toward the end of the experiment the lowest leaves had
turned to a bright orange color. No evidence of purple veining
appeared in these plants. The fact that the plants undoubtedly
had built up a fair reserve of phosphate before being placed on
treatment meant that the deficiency never was as severe as has
been described elsewhere. Nevertheless, it was of sufficient
severity to influence the fruiting. A good set of fruit was ob-
tained, but none developed normally, although they did not ab-
scise except on the boron-deficient plants. Shiny brownish-black
spots appeared on the blossom ends of all fruits on the phos-
phate-deficient plants. These enlarged rapidly until the lower
half was affected. The appearance of the spots was somewhat
similar to blossom-end rot, except that these spots were darker
in color and did not dry out. This is apparently a symptom of
phosphate deficiency under high nitrate conditions.
The sulphate-deficient plants (Series Z) showed deficiency
symptoms, although these were not of any real severity. Plants
of this series produced the greatest weight of fruits, and these
fruits were of the highest quality (visually) of any in the test.
The plants produced many lateral shoots, but in general were
tall and rangy in appearance. Leaves were of a distinctly light
green color, and deficiency patterns showed on the oldest leaves.
This deficiency symptom developed as large, white intervenal
spots, which developed progressively up the stalk from the low-
est leaves.

PRESENTATION OF GROWTH DATA AND DISCUSSION
Stem elongation measurements were taken of all plants on
the day that differential anion treatments were started, and
periodically thereafter until the experiment was terminated.
Growth rate curves were plotted from these data and are pre-
sented in Figures 1 to 7, each representing a main-plot anionic
balance treatment grouped so that all 4 boron sub-treatments

Florida Agricultural Experiment Station

appear in each figure. Each point fixed on the curves represents
a simple average of the growth rates of the 2 plants given that
treatment. These figures will be discussed along with the data
on the interactions. In addition, the total stem elongation from

0 6 13, 20 30 -
DAYS FROM STARTING OF ANIOa TREATMENTS
Fig. 1.-Daily rate of growth of the apical meristem of plants of
Series T. The differential boron treatments were started on the 12th day,
as indicated by the arrow in this and succeeding figures.

0 6 13 20 30 40
DAY/ FROM STARTING OF ANION TE.TrmENTrS
Fig. 2.-Daily rate of growth of the apical meristem of plants of Series U.

Functional Relationships Between Boron and Anions 11

the time the differential anion treatments were started is pre-
sented in Table 2, along with the other data.
Just before the experiment was terminated a count was made
of all developing shoots (including the terminal meristem) on
each plant. This information also appears in Table 2.
The balance of the data in Table 2 consists of fresh weights

DAYS FROM SrTRTI/N OF ANION TRXATMCrTS
Fig. 3.-Daily rate of growth of the apical meristem of plants in Series V.

0 6 13 20 30 40
DAYS FROM SrARTIN OF AoF oI TREArMENTS
Fig. 4.-Daily rate of growth of the apical meristem of plants in Series W.

--r,-

Florida Agricultural Experiment Station

of various plant tissues. All are self-explanatory except that
leaf tissue includes the petioles and growing points.
Each set of data appearing in Table 2 was analyzed, using the
analysis of variance with split-plots. The method, together with
the F-values found, is indicated in Table 3.
In making all quantitative comparisons in the balance of this
paper, significant differences were determined by calculating the
standard error of totals and multiplying this by the V2 x t,
according to standard statistical procedure (7). This gives about

DAYS FROM STARTING OF ANION TREATrC'Nrs
Fig. 6.-Daily rate of growth of the apical meristem of plants in Series Y.
V J-------------------------------------- ---

Fig. 6.-Daily rate of growth of the apical meristem of plants in Series Y.

Functional Relationships Between Boron and Anions 13

3 times the standard error in most cases. Any totals which
differed from each other by more than this value were adjudged
to be significantly different, with odds of 19 to 1. For con-
venience, in every comparison the treatments to be compared
have been so grouped that the first listed treatment in each
group is significantly superior to all treatments in lower groups.
This method facilitates rapid comparisons and is usually ade-
quate to a good understanding of comparisons, particularly when
differences among treatments are relatively large, as was found
to be the case in this experiment.
Photographs of representative plants from each treatment,
taken at the end of the experiment, are presented in Figure. 8.
They are arranged in graphic sequence, so that this figure can
be used to supplement the data and discussion.

EFFECT OF ANIONIC BALANCE
With every set of data there were differences significant at
odds higher than 99 to 1 that were due to variations in the
anionic balance (see Table 3 for F values). All data in Table 4
can therefore be compared for the purpose of studying the
effect of anionic balance.
Whole Plant.-With the whole plant fresh weight data the
series was grouped as indicated in Table 4. These data were
calculated in terms of dekagrams for convenience (1 deka-
gram=10 grams).

r .. ..... :" '--

150

Or

I I C S.R/ S Z

i No Bo 'Oo -
0.OOSp.m --
A O.,p.p. -m. -
0 6 13 20 30 40
DAYs FRoM STARTING OF ANION "RCAT/Me4NrS
Fig. 7.--Daily rate of growth of the apical meristem of plants in Series Z.

Florida Agricultural Experiment Station

The most spectacular effect, as might be expected, was due
to the level of nitrate. Series U, with 16 m.e. of nitrate and
1 each of phosphate and sulphate per liter, and Series T with
6 m.e. of each anion, both produced more tissue than did other
treatments. Both series in Group II, while they received more
nitrate (9 m.e.) than did Series T, were completely deficient in
one of the other anions. Series Y received no phosphate and
Series Z no sulphate. Both series in Group III received but
1 m.e. of nitrate and Series X, all alone in Group IV, received
a solution completely devoid of nitrogen. The level of nitrate
in the substrate was therefore the determining factor in the
production of plant tissue.
Fruit Tissue.-There were some shifts in the groupings when
different plant parts were considered separately. These shifts
tend to reveal the requirements of the different plant organs
for the various anions.
For example, the groupings where fruit tissue weights alone
were analyzed are listed in the second column of Table 4.
In these groupings Series Z has moved up to Group I, Series
U has moved down to Group II, and Series Y has moved down to
Group III. The linkage of phosphate and nitrate concentrations
with fruiting is evident, since in each of these shifts it can be
used to explain the shift. Plants receiving no phosphate (Series
Y) dropped down into the same group as those receiving no nitrate
(Series X). Plants receiving very low phosphate but very high
nitrate (Series U) dropped down into the same group as those
receiving very low nitrate (Groups V and W). And, finally,
plants receiving high nitrate and high phosphate (Series Z),
even though grown on solutions completely deficient in. sulphates,
moved up in fruit yields to the same group as those plants which
received the "balanced" anionic solution (Series T). The low
fruiting of nitrogen-deficient plants appears to be a general ex-
pression of low plant vigor. The effect of phosphate deficiency
would appear to be more specific than that, however, since plants
of Series U and Series Y were strong and vigorous. Phosphate
deficiency was certainly directly linked to fruiting. Finally,
there was certainly no indication that sulphate is required in
any quantity for fruit development. A good balance and adequate

Fig. 8.-Photographic chart of representative plants of each sub-plot
treatment. Camera distance, light source, film and print exposure and
developing times all held constant, so that not only plant sizes but also leaf
shade can be compared. (Note the dark leaves on Series Y, for example.)

SERIES T

SERIES U

SERIES V

SERIES W

SERIES X

SERIES Y

SERIES Z

NO 0.005
BORON p.p.m.
BORON

0.5 10.00
p.p.m. p.p.m.
BORON BORON

TABLE 2.-QUANTITATIVE DATA FROM THE BORON-ANIONIC BALANCE SERIES.
Two Replications, Blocks A & B. All Weight Data are on Fresh Tissue Basis.

supply of both phosphate and nitrates is required for adequate
fruit production. This not only is in agreement with all in-
formation and conclusions reached in the past, but serves also
to indicate that the method of study used here is sensitive to
such factors, lending weight to other comparisons made with
this series of plants.
Leaf Tissue.-With respect to the weights of leaf tissue pro-
duced, the groupings also are listed in Table 4. In these compari-
sons the predominant effect of nitrate level is very evident. The
fact that both Series Y and Z were inferior to Series T indicates
that the plants receiving solutions deficient in either sulphate
or phosphate did not produce as much leafage as did cultures
where both of these ions were present, even though the nitrate
concentration was somewhat lower in the latter. The fact that
Series U led all the rest by a good margin, however, indicates
that nitrate concentration was by far the most important anion
concerned with leaf tissue production.
Stem Tissue.-The data on stem tissue are of some interest.
The groupings are also included in Table 4. Nitrate concentra-
tion is obviously the most effective anion in the development
of stem tissue, undoubtedly a reflection of the quantity of leaf
tissue produced. However, the fact that the stem becomes a
secondary storage tissue when fruiting is depressed is evident
from this grouping. Series Z, with a large crop of fruit, had
relatively light, spindly stems. Series U and Y, fruiting lightly,
produced heavy stems. Again, Series T, on "balanced" solution,
produced a strong stem. It will be noted throughout the data
that regardless of which organ is being considered, plants of
this series were always well up toward the top.
Root Tissue.-The series are grouped in Table 4 with respect
to root tissue. Series Y, producing very little fruit tissue, and
Series U, producing lightly in comparison to the amount of leaf
surface, produced heavy root systems, an indication that a con-
siderable amount of carbohydrates moved to the roots. Series Z,
heavy fruiting, had smaller roots.
Plant Height and Number of Shoots.-The anionic treatments
are also grouped in Table 4 according to increase in height in
centimeters from the time the differential anion solutions were
first applied and according to the number of aerial meristems
produced.
The height increase measurement was complicated by the fact

Florida Agricultural Experiment Station

that there were differences in the number of side-shoots de-
veloped. Perhaps the most interesting observation which can
be made concerns Series Z, which produced the highest yield
of fruits and still was in Group I for vine height. These plants
also produced as many side-stems as did other high nitrogen
cultures. This latter characteristic seemed related to nitrogen
concentration alone- on all plants receiving 6 m.e. or more
of nitrogen per liter the number of aerial terminal meristems
varied from 5 to 8. The number varied from 3 to 5 with 1 m.e.
of nitrogen, and from 1 to 3 where no nitrogen was supplied
(Series X).
EFFECT OF BORON CONCENTRATION
With all growth criteria measured (except number of side-
shoots) there were differences among boron treatments signifi-
cant at odds greater than 19 to 1. These data (Table 5) can
therefore be examined more closely to study the effects of boron
level.
Whole Plant.-Grouping the treatments as before, when whole
fresh plant weights are considered, the data permit drawing
definite conclusions. All treatments differed significantly from
all others (odds 19 to 1). 0.005 p.p.m. boron was not enough
for optimum growth, and 10.0 p.p.m. was obviously too much
boron.
Fruit Tissue.-With respect to weight of fruits produced, the
grouping was somewhat different. At the range of severity of
boron toxicity in this test fruit development was not affected
within the limits of experimental error. The other treatments
ranked as with whole plant tissue. An inadequate boron supply
can easily limit production of fruit, as often demonstrated.
Leaf Tissue.-Considering leaf tissue, the effect of boron
toxicity as observed symptomatically is supported by the data
in Table 5. The relatively moderate toxicity produced in this
test did not destroy the leaf tissue until fruits were partially
developed, since the oldest leaves were affected first.
Stem Tissue.-Where boron toxicity was indicated, leaf tissue
was light and fruiting relatively heavy. Probably a combina-
tion of these factors was responsible for the fact that stems
were also light under these conditions. Fruit development
utilized most of the sugars produced by the damaged leaves.
It should be noted that plants receiving no boron produced
small amounts of stem tissue. This reflects principally the

Functional Relationships Between Boron and Anions 21

TABLE 5.-EFFECT OF BORON TREATMENTS ON VARIOUS GROWTH DATA.
THE BORON LEVEL TREATMENTS ARE SO GROUPED THAT THE HIGHEST
LISTED IN EACH GROUP IS SIGNIFICANTLY SUPERIOR (ODDS 19 TO 1) TO
ALL TREATMENTS IN LOWER GROUPS.

overall dwarfing of the plants. The fact that boron deficiency
has often been reported as producing plants with thick stems
is discussed later in this paper in the interaction data.
Root Tissue.-A grouping with respect to root tissue weights
gives a picture probably based on factors similar to those dis-
cussed in connection with stem tissue. The amount of root

Florida Agricultural Experiment Station

tissue produced seemed to be largely an expression of plant
vigor.
Plant Height and Number of Shoots.-The effect of boron
deficiency in killing the growing point is reflected in the data
(see Table 5), as is also the lesser effect of a toxic concentration
in slowing down the general rate of growth. Boron level had
no significant effect on the number of shoots produced, the
F value barely missing significance at the 5 % point, as indicated
in Table 3.
EFFECT OF THE INTERACTION-BORON
CONCENTRATION X ANIONIC BALANCE
It is by means of the significant variations from the effects
listed above that something more of the functions of boron in
plant growth can be deduced. It is possible to measure the
effects of different boron levels within each anionic balance
series, and vice-versa, since the interaction was found to be
significant at the 1 percent point for each growth criterion
analyzed. In this discussion only those interaction comparisons
will be discussed which show significant variations from the
independent analyses for boron levels or anionic balance series
as presented above. All of the information on interactions is
listed in Tables 6-19 in the appendix.
In considering the effect of boron supply on anionic balance,
the anion treatments may be compared at each boron level. The
data on this comparison are given in Tables 6 to 12. For
example, in comparing data for whole plant weights, where no
boron was supplied the anionic balance series group is listed
in Table 6 in the appendix. This grouping can be compared with
that listed in Table 4, where the series are compared without
regard to boron level. It may be seen that Series U, Y and W
have each dropped 1 group in the listing where no boron was
applied. Series U is high in nitrate, low in phosphate and
sulphate; Series Y is deficient in phosphate, medium high in
nitrate and sulphate; and series W is low in both nitrate and
phosphate. It will be noted that, in each case, plants which
were injured most by complete boron deficiency were also either
completely deficient in or very low in phosphate. This might
tend to indicate that, to some degree at least, phosphate can
substitute for boron (as borate). Since both of these radicals
are good buffers, it is possible that they serve this function in
common in plant tissues.
With adequate boron (0.5 p.p.m.) which might be considered

Functional Relationships Between Boron and Anions 23

as a "normal" treatment in this respect, it will be noted that
the same 3 series (U, Y and W) have moved upward in the
groupings again, with both Series U and Series W 2 groups
higher and Series Y up 1 group. This lends some support to the
theory that 1 function of boron might be that of a buffer. When
boron was supplied as borate in adequate quantity, less phos-
phate was required than was otherwise the case, as measured
by the fresh tissue weights produced. Under these conditions
the influence of nitrates on growth was the limiting factor.
The data on separate tissue analysis and terminal growth
(Tables 7 to 12) serve to emphasize these relationships, and
need not be discussed further.
To consider the effect of anionic balance on boron requirement,
it is possible to study the interaction by comparing tissue weights
within anionic balance series. Figures 1 to 7, where growth
rates are plotted, illustrate this type of interaction comparison.
When the effects due to anionic balance are not taken into
account, the boron levels group as listed in Table 5, with each
boron level falling into a separate group when the whole plant
tissue weights are considered. In Table 13 it can be seen that
with Series V and X, however, no boron treatment proved sig-
nificantly different from any other all fell in the same group.
Figures 3 and 5 also emphasize that with these anion treatments
no boron deficiency developed. In all other series 0.5 p.p.m. was
significantly superior to no boron and in Series U and T it was
superior to 0.005 p.p.m. as well. This indicates strongly that
when nitrogen is high boron deficiency can be very severe.
Where no nitrogen was supplied no boron deficiency symptoms
appeared and no differences were found in tissue weights or
growth rates.
With respect to boron toxicity, symptoms developed first and
were most severe where phosphate was low and nitrate high
(Series U and Y). In Series Z (relatively high in both nitrate
and phosphate), boron toxicity was less severe, both as deter-
mined by plant weights and as observed during the growing
period.
The analyses of fruit tissue data serve to emphasize these
conclusions (see Table 14). Series U and Y came through with
practically no fruit when boron was omitted. Fruits that
formed early abscised. Group Z, receiving the same quantity
of nitrate as Group Y but ample phosphate in addition (Y was
deficient in phosphate), held and developed its fruit, although

Florida Agricultural Experiment Station

many showed the corking typical of boron deficiency. A similar
condition held in comparing Series V and W (both low in
nitrate). Series V showed no indications of boron deficiency
when no boron was added. Series W, while it held its fruit
fairly well, definitely showed injury, both by visual symptoms
and by analytical data. This effect was also evidenced in growth
rates, as can be seen by comparing the no boron treatments in
Figures 3 and 4.
Data on leaf, stem, root and plant height analysis roughly
support these conclusions, and a detailed discussion is therefore
omitted. Tables 15 to 19 give the other interaction groupings.
It should be remembered in considering the arrangement in
these tables that the highest listed treatment in each group is
significantly superior to the highest in the next listed group.
Calculations for these groupings were made from the data in
Table 2.
A brief study of the growth rate curves (Figures 1-7) will
give almost the entire picture, despite the fact that side-shoots
were permitted to develop, and undoubtedly affected the growth
rates of the terminal meristems. In Series Y (phosphate de-
ficient) and U and W (phosphate low), the no boron treatment
curve broke sharply downward between the 13th and 20th days
from the time the differential anion treatments were started,
while the curves for the other boron treatments continued to
climb or held level. (In these figures, the arrow inserted at the
12th day indicates when the differential boron treatments were
started.) In the other anion series where boron deficiency de-
veloped (Series T and Z) there were ample supplies of both
phosphate and nitrate, but the break in the no boron curve came
later.
Therefore, growth rate curves and quantitative data show
definitely that boron nutrition is linked with both phosphate and
nitrate nutrition. Boron deficiency develops severely with a
high nitrate supply, regardless of the phosphate level, and with
a low phosphate supply, regardless of the nitrate level.
The linkage with nitrates tends to support previous findings
that boron is essential to normal protein synthesis through its
effect on the utilization of carbohydrates.
The linkage with phosphates would seem to be of an entirely
different character. It is suggested here that the borate and
phosphate ions can act interchangeably as essential juice buffers,
or possibly by removing cations from solution which form rela-

Functional Relationships Between Boron and Anions 25

tively insoluble salts with these radicals. The former possibility
would appear to be the most likely, but possibly both are true
to some extent.
CONCLUSIONS AND SUMMARY
A set of tomato plants (variety Rutgers) was grown in pure
quartz sand culture by the constant drip method. By use of a
factorial split-plot design and the analysis of variance, the data
showed significant interactions interpreted as follows:
1. Between Nitrate Level and Boron Requirement.-Plants
grown with solutions containing ample nitrates required many
times more boron than did nitrate-starved plants. This informa-
tion was interpreted as being in support of the theory that boron
is functional in normal protein metabolism probably through a
direct effect on carbohydrate utilization in normal metabolic
processes.
2. Between Phosphate Level and Boron Requirement.-Plants
grown with solutions deficient in phosphates require more boron
than do plants receiving ample phosphates. The theory is pre-
sented that the phosphate and borate ions may function inter-
changeably as essential juice buffers, or in precipitating out
excess cations which form relatively insoluble salts with these
ions, or in both of these functions.
These findings may well have general practical application,
although it has not yet been attempted to correlate them with
field plot work.
Many of the crops with high nitrogen and high potash re-
quirements, such as alfalfa, the various vegetable crop plants
of the genus Brassica, and sugar and garden beets, are more
seriously effected by a boron deficiency than are crops of lower
nitrogen and potash requirements. A realization that high ap-
plications of these major nutrient materials will aggravate any
boron deficiency which may be present should help to avoid
such a difficulty.
With relation to the boron-phosphate relationship found, it
would indicate that boron deficiency might be expected to limit
growth on soils naturally low in phosphate. This might be
expected regardless of nitrogen and potash levels.

13. STEWARD, F. C., and C. PRESTON. The effect of salt concentration upon
the metabolism of potato discs and the contrasted effect of potas-
sium and calcium salts which have a common ion. Plant Physiol.
16: 85-116.